Setting up environment variables

What would be the best way to set a bunch of system-wide environment
variables(I have about 1000 lines) from a script instead of GUI?

I tried using 'setx /m' but it becomes to cumbersome.

e.g:

setx /M PFI="c:\Program Files"
setx /M SRO="%SystemRoot%"
setx /M S32="%SRO%\system32"

setx /M P0=%PFI%;%SR%;%S32%
....
etc,etc,etc...

Thanks